Ram air operated fuel pump



May 1, 1951 w. K. DEACON RAM AIR OPERATED FUEL PUMP Filed March 14, 1946ammo/r1154 WALTER k. DEACON Patented May 1, 19 51 r --UNITED STATESPATENT OFFICE RAM AIR OPERATED FUEL PUMP Walter K. Deacon, United StatesNavy A plication March 14, 1946, Serial N0. 654,484

(01. GIL-35.6)

(Granted under the act of March 3, 1883; as

3 Claims.

amended April 30, 1928; 370' 0.- G. 757) This invention relates to ramjet engines and in particular to the fuel system therefor.

It has been recognized that the fuel requirements for combustion in aram jet engine vary directly with the square root of the dynamic'head orram pressure created by the forward velocity at any given altitude andalso that the fuel flow through a nozzle also varies with the squareroot of the pressure drop thereacr'oss. Itis apparent, therefore, thatthe ram pressure becomes a convenient fuel pressure source to deliverfuel in accordance with engine requirements. When used'di'rectlyhowever, it has the disadvantages that with an increase in altitude at agiven velocity the fuel requirements decrease at a greater rate than theram pressure available for a given Mach number thus tending towardenrichment, and at low speeds the ram pressure available is notsufiici'ent to insure optimum fuel atomization' or to compensate forsudden pressure changes in the combustion chamber.

This invention obviates the disadvantages ahcve mentioned and has,therefore, as one of its objects, the provision of a ram jet fuel systemwhich delivers the optimum amount of fuel under the variable conditionsof velocity and altitude.

Another object is the provision of a ram jet fuel" system which utilizesavailable an pressures for delivering fuel to a combustion chamberthereby eliminating cumbersome pumping d'eviceswhi'cn require fortheiroperati'o'n a source of energy carried by the unit, thus decreasingthe complexity and overall Weight thereof.

Another object is the provision of a rain jet fuellsyste'm whichutilizes air at ram pressure to pump fuel at a pressure'in excessofcombustion chamber fuel pressure requirements.

Another object is the provision of a rain. jet fuel systemwhichincorporates a fuel pump operable by ram pressure capable of deliveringfuel at a pressurehigher than ram pressure.

Further objects, advantages, and salient features of the invention willbecome apparent from a consideration of' the description to follow, theaccompanying drawing and the appended claims} The accompanying drawingisaside' elevational' view, partly insection, of an embodiment of theiriyention;

Referring tothe drawing, i resp'resents a fuel tank from' which it isdesired to deliver fuel to ,conduit 2, the latter being connectable toany -suitable fuel nozzle system in a ram jet combustiorr chamberillustrated" diagrammatically at H or" other engi'ne; Referencecharacter 3' repr'e" sents a fuel pump and 321' its driving motor and 255 a regulator for controlling fuel delivery to conduit 2.'

Fuel pump 3 and motor to comprise apair of motor cylinders i, 4a havingreciprocating pis tons 5, 5a therein connected respectively by pis tonrods 6, 6a to pump pistons F, la which recipro cate in" cylinders 8, 8a.Diaphragms 9, Sa and H], Ito, provide fiuid seals" for the pistons inthe motor and pump cylinders, respectively. Ahell crankhaving arms Ii,la interconnects these units by 13111 and slot connections so that theyare constrained to operate in opposite directions;

The motor is operated by air flowing in conduit 12 the end of which islocated in any convenient position. where it may receive air at rainpressure as shown at 12c. Operation of the respective motor pistons55,50, is eoiitroll'ed by a valve {3 having inlet valves l4, Ma andexhaust'ifalves I5, l5a. These alves have sliding movement on valve stemit, the valves of each pair ,eiiig" urged toward each other by suitahlecompression springs H; Ila, i8 and i811. The lower end of valve stem I6is" connected to bell crank arii'i H by link 2! and a toggle actuatorcomprising a pair of relatively moi/awe arms 22, 2'3 and an overcenterspring 24". p

In the position or parts, as shown, aif' fiofri conduit [2 enters valve13 and then passes through intake valve M, which is held open by theupper shoulder on; valve stem [6, and thence to cylinder 4, urgingpiston 5 downwardly, exhaust valve [5 being held closed by spring ['81Since piston 5a is moving upwardly at this time the air in cylinder 4amust be exhausted which is effected through exhaust valve [5c heldoffits seat by the valve stem shoulder thereunden The air then flows" tosurrounding air at static pressure through conduit I9. Whenpiston 5approaches the end of its stroke, arm 22, operated by H, reaches aposition in line with arm '23. This stretches spring 24 to its maximumextent and as arm 22 mo'ves beyond the inline position spring 24 snaps"arm 23 downwardly. At this point spring I! urges inlet valve I 4 to itsseat and the valve stem shoulder abo've valve [4a opens'tl'ie' latter toad'mit air to cylinder 4awhich is" now"at the top of its stroke. Exhaustvalve 15 is also closed under urge of spring [to and exhaust valve 15 isopened by the valve stem collar thereabove. As piston 5a movesdownwardly, arm 22' moves upwardly to its overcenter position at whichpoint 23" snaps back to the position sh'o'wn'at which point the" cycleis com pletedlf .i a

' Asthe" motorpisfons reciprocate; pump pistons I, la. receive fuel fromtank I through inlet check valves 25, a, respectively, and deliver it toconduit 21 through check valves, 26, 26a. In order that the deliverypressure may be higher than ram pressure, the motor piston areas arelarger than the pump piston areas hence any desired increase in deliverypressure over ram pressure may be achieved by suitable selection of thisarea ratio.

To obviate surges in fuel delivery pressure which might occur at or nearthe ends of the piston strokes a surge motor and pump 28 is provided.This comprises a closed motor chamber 29 having a diaphragm 30 subjectedto ram pressure through conduit 3i, and a pump chamber 32 having adiaphragm 33 connected to diaphragm 30 by rod 34. A conduit 35 providesliquid communication between chamber 32 and conduit 21. The area ratioof diaphragm 30' to diaphragm 33 is slightly less than the ratio ofpiston 5, or 5a to I, or la hence the surge pump is inoperative duringconstant fuel pressure delivery but when the fuel pressure tends todrop, diaphragm 30 temporarily operates pump diaphragm 33 to maintaindelivery pressure substantially constant.

The fuel delivered by 2?, in the system so far described, may beconducted directly to a combustion chamber 5| if so desired, however, inmany installations it will be more desirable to further control themetering characteristics of the pumping system. To this end, a flowcontroller 50 may be provided, this device comprising a chamber 36having a diaphragm 31 forming one side thereof and operably connected tocontrol valve 38. One side of diaphragm 31 is subjected to ram pressurethrough conduit 46 and a spring 39 aids ram pressure in urging diaphragm37 to the left against delivery pressure. An adjustment to regulate themetering characteristics of valve 38 such as externally threaded valvestem and seat 3811 adjustably secured in tapped hole 33b in wall ofchamber 36 and secured with locknut 380 may also be provided. Themetered fuel, after entering chamber 42 is delivered to conduit 2 whichmay be connected to any fuel delivery system for a combustion chamber.

To also provide control under variable altitude a variable orifice 43may be incorporated in conduit under control of a suitable barostatdevice 44 and an orifice 4| for controlling the pressure drop betweenchamber 36 and ambient static pressure. The evacuated barostat beingresponsive to air pressure changes moves valve 43 toward its closedposition with increase of altitude thus reducing the pressure in chamber36 which in turn permits delivery pressure to move valve 38 toward itsclosed position. This reduces the quantity of fuel delivered to thecombustion chamber which is necessary since the mass flow of air throughthe combustion chamber decreases with increase in altitude,assumingvelocity to be constant.

From the foregoing description it becomes apparent that at low rampressures which are normally insufficient to directly deliver fuel atoptimum pressure, this invention delivers fuels at any desired pressureabove ram pressure depending on the design of the areo ratio of themotor pistons to pump pistons. As velocity increases and hence thequantity of air flowin to a combustion chamber increases, requiringgreater increase in fuel flow, the ram pressure alsoincreases which inturn will render the pump operable to deliver fuel at the higherpressures and hence higher quantities requisite for proper combustion.The final metering being under control of the pressure drop between ramand static pressures provides a means to regulate the optimum fuel flowfor variation of velocity at any fixed altitude. To further control flowat variable altitude a barostat augments the previous controls.

The fuel system described, being automotic in operation under variableflight conditions is well adapted to aircraft or other installationswhere no human pilot or operator accompanies the craft, such for exampleas guided missiles. It is, of course, not so limited and may be usedalso in operator controlled vehicles of any type which have speedcharacteristics sufficient to establish the requisite ram pressures forits operation.

While a single embodiment has been described it is apparent that othermodifications will occur to those skilled in the art and it will beunderstood that the illustrated construction is not presented by way oflimitation but that the invention comprehends all constructions comingwithin the scope of the appended claims. The invention described hereinmay be manufactured and used by or for the Government of the UnitedStates of America for governmental purposes without the payment of anyroyalties thereon or therefor.

What is claimed is:

1. In a device of the class described the combination comprising; aconduit open forwardly to receive ram air, fluid motor means connectedto said conduit for operation by said ram air, a fuel delivery line, afuel pumping means driven by said fluid motor means, said fluid motorand pumping means having operative pistons of relative diameters suchthat the fuel is delivered to said delivery line at a pressure in excessof said ram pressure, a chamber having a movable wall, said chamberbeing connected to said conduit for directing ram pressure to said wall,and a fuel accumulator in communication with said delivery line having asecond movable wall, said movable walls being connected for simultaneousmovement in response to ram air and fuel delivery pressure tomaintainsubstantially constant fuel delivery to said delivery line between pumpstrokes.

2. In a fuel feed system for ram jet engines the combination of aconduit opened forwardly to receive air at ram pressure, a two-cylinderair motor with opposed pistons connected to said conduit to be operatedby said ram pressure, a reciprocating piston in a cylinder for pumpingfuel connected to each of said motor pistons, the cross sectional areaof the pumping pistons being less than the cross sectional area of themotor pistons whereby the pump delivery pressure is in excess of rampressure, fuel supply means and fuel delivery means connected to saidpumping pistons, a fuel accumulator with a flexible wall responsive toram air pressure in said conduit and connected to said fuel deliverymeans, and metering means in said delivery means for controlling therate of fuel delivery to a combustion chamber, said metering means beingresponsive to variations in ram air pressure and ambient atmosphericpressure.

3. The device as set forth in claim 2 in which said fuel accumulator hasa first flexible wall responsive to ram air pressure on a secondflexible wall connected thereto and said second flexible wall and saidfirst flexible wall having a ratio 5 of slightly less than the ratio ofareas of said Number motor pistons to said pumping pistons. 1,888,749WALTER K. DEACO-N. 2,233,307 I 2,274,224 REFERENCES CITED 5 2,402,363The following references are of record in the file of this patent:

Number UNITED STATES PATENTS 625,104 Number Name Date 10 799,253

1,369,672 Koenig Feb. 22, 1921 6 Name Date Urquhart Nov. 22, 1932 DodsonFeb. 25, 1941 Vickers Feb. 24, 1942 Bradbury June 18, 1946 FOREIGNPATENTS Country Date France Apr. 19, 1927 France Mar. 27, 1936

